The renewable energy sources list includes energy sources such as solar energy, wind energy, geothermal energy, hydropower, and biomass. By reading this article you can learn basic things about these five renewable energy sources. Renewable energy is very important because it offers environmentally friendly alternative to using fossil fuels. It can also improve our energy security and our energy independence, and most of all lead the world towards the clean and safe energy future. Let us start the story about the renewable energy sources with the most abundant form of energy on our planet, namely the solar energy.

SOLAR ENERGY

Solar energy is the most abundant energy source on our planet but the world currently uses a negligible fraction of the totally available solar energy. Solar energy technologies are still in the early development phase, and they will certainly take some time before reaching adequate levels in terms of efficiency and costs.

Solar energy is environmentally friendly renewable source of energy. Unlike fossil fuels, harnessing solar energy doesn't result in harmful CO2 emissions. Our Sun is virtually unlimited source of energy that could (with the right technology) supply with ease our current as well as the future energy demand, for instance covering just 4% of the world's desert area with photovoltaics could supply all of the world's electricity.

Solar energy is still a rather expensive renewable energy option. Solar panels are connected with relatively high costs, and their efficiency is still unsatisfying. Solar energy definitely needs to improve deficiency and costs in order to challenge fossil fuels on global level. There are many ongoing solar researchers and hopefully science will soon find solutions to improve economics and efficiency of solar power technologies.

In 2008, solar energy accounted for less than 0.02% of the world's total energy supply, way too little, given its enormous potential. Despite this small number solar energy sector is constantly growing, for instance global installed solar photovoltaic power capacity grew by 44 percent in 2009. The largest photovoltaic market in the world is Germany.

Solar energy market is constantly growing in United States, and if the current pace continues solar power's contribution could grow to 10% of the nation's power needs by 2025. There is also a strong public support for new solar energy projects in United States. California is the leading U.S. state in solar energy with the installed capacity of over 500 megawatts of solar power.

Solar power plants are a large collection of interconnected solar panels. The largest solar power plant in the world is located in California, with the capacity of 354 MW. The main disadvantage of solar power plants is that they have high initial costs, and require huge area of space.

In general, solar power plants have positive environmental impact. Harnessing solar energy doesn't contribute to climate change, acid rains or any form of pollution. The only downsides are: manufacturing solar panels (because some hazardous materials are involved), and the fact that huge solar power require lot of land for construction, and lot of water for cooling purposes which could eventually lead to damage to some nearby ecosystems.

WIND ENERGY

People were using wind energy for more than 5000 years to propel sailboats and sailing ships. These days wind energy is mostly used to generate electricity by using wind turbines. Wind power is one of the fastest growing renewable energy sectors. Wind farms are no longer being built only on land but also offshore, and offshore wind energy could in years to come become dominant way of harnessing wind energy.

Wind energy is environmentally friendly renewable energy source that does not contribute to climate change or air pollution. Over the years, wind power has also become more cost competitive, and is currently one of the few renewable energy sources that could actually compete with fossil fuels in terms of economics.

Wind energy is intermittent energy source, and in times when wind doesn't blow we need another backup energy option to ensure constant energy supply for customers. Large wind turbines with huge blades can kill many birds if not equipped with radar. Sometimes it is difficult to integrate wind turbines into existing environment because they can disrupt visual effect of certain landscape.

At the end of 2009 globally installed wind power capacity was 159.2 gigawatts, and even despite the global recession in 2009 wind energy sector experienced large growth of 31%. World's largest wind power consumer is United States, followed by Germany, Spain, China, and India.

Wind energy is very popular renewable energy source in United States. In 2009, despite the recession U.S. increased its wind power capacity by adding more than 10,000 megawatts to its power grid, further strengthening its position as global leader in wind energy installations. Among US states Texas leads the way with more than 10,000 megawatts of installed wind power capacity.

Wind farm is basically a group of interconnected wind turbines on one location which is used for production of electricity. The world's first wind farm was installed on the shoulder of Crotched Mountain in southern New Hampshire in December, 1980. Currently the world's largest wind farm is The Roscoe Wind Farm, with the output of 780 MW, in the state of Texas.

Wind energy has overall positive environmental impact since there are no emissions involved. As already said above large, fast rotating blades can kill many birds if not equipped with radar, large wind turbines can also create noise pollution which can have negative effect on wildlife in nearby area.

GEOTHERMAL ENERGY

Geothermal energy refers to power extracted from heat stored in the Earth. Where does this heat originate from? It all started long, long time ago when our planet originally started its formation, from radioactive decay beneath the Earth's surface, volcanic activity, and also from solar energy that was absorbed at the surface. The first geothermal energy use was for bathing, but today geothermal energy is mostly used to generate electricity, and in some countries also for heating purposes in form of geothermal heating.

Geothermal energy is renewable energy source that cannot be depleted since earth is in constant state of producing heat, and it does not produce harmful carbon emissions nor it contributes to air pollution like fossil fuels (coal, oil, and natural gas do). Geothermal energy is clean, cost effective, reliable, sustainable, and environmentally friendly source of energy. Unlike solar and wind energy geothermal energy doesn't suffer from intermittency issue, and once built geothermal power plants offer extremely reliable clean energy solution.

High installation costs are probably the first thing when talking about the cons of renewable energy. Geothermal power plants are very expensive to be built costing twice as much compared to natural gas power plants. High construction and drilling costs are the main reason why geothermal energy isn't economically viable option in all corners of the world, but only in areas with suitable amount of hot rocks at just the right depth for drilling. Once the drilling technologies become more technologically advanced geothermal energy will likely become much more competitive to fossil fuels.

Geothermal energy is renewable energy sector that is quickly expanding, and in the last couple of years global geothermal capacity has increased by more than 20%, with around 10,715 megawatts (MW) of geothermal capacity installed worldwide. 10,715 megawatts (MW) projects growth to 18,500 MW by 2015.

United States is global leader in installed geothermal energy capacity with 3,086 MW of installed capacity coming from 77 geothermal power plants. California is the nation's leader with more than 2500 MW of geothermal energy production capacity but Nevada is quickly closing the gap. The first U.S. geothermal power plant was opened at The Geysers in California in 1960. According to current estimates installed geothermal capacity in the United States could exceed 15,000 MW by 2025.

Three basic types of geothermal power plants are: 1.dry steam plants where steam is piped directly from a geothermal reservoir to turn the generator turbines. 2.flash steam plants that takes the high-pressured hot water from deep inside the Earth and convert it to steam to turn the generator turbines. 3.binary cycle power plants that transfer the heat from geothermal hot water to another liquid, and then the second liquid is turned into the steam that turns the generator turbines.

As said before geothermal energy is environmentally friendly source of energy. Existing geothermal electric plants emit an average of 122 kilograms (269 lb) of CO2 per megawatt-hour (MW•h) of electricity, an amount negligible compared to fossil fuel power plants. Harnessing geothermal energy has minimal land and freshwater requirements. The only potential hazard is the fact that fluids drawn from the deep earth carry a mixture of gases, such as carbon dioxide (CO2), hydrogen sulfide (H2S), methane (CH4) and ammonia which can (if not treated properly) add to global warming, air pollution, and acid rain.

HYDROPOWER

Hydropower is renewable energy source that has been used for many hundreds of years in form of waterwheels and mills. Hydropower is today the most important renewable energy source on global scale supplying around 20% of world's electricity.

Hydropower is renewable energy source that doesn't pollute our planet with harmful greenhouse gas emissions like fossil fuels do. Hydropower plants have long lifespan, and relatively low maintenance costs since almost everything is automated. Hydropower also doesn't suffer from intermittency issue like wind and solar power do, and ensures constant supply of energy. Hydropower is also very efficient energy source.

Hydropower can sometimes cause significant environmental damage, especially when constructing huge hydroelectric power plants (Three Gorges Dam). The negative effects can even lead to earth quakes, erosion, landslides like this was case in China with Three Gorges Dam. Large hydroelectric power plants have high initial costs, and these projects usually take couple of decades before returning the investment.

Hydropower has very long tradition in United States, and thus it is no surprise that hydropower is currently the most important renewable energy source in US, accounting for around 8% of nation's electricity. Only three countries in the world produce more hydroelectricity than US, China, Canada and Brazil. US currently has more than 2000 hydroelectric power plants, with the biggest located in the Northwest, the Tennessee Valley, and on the Colorado River.

As already mentioned above hydropower is the most important renewable energy source on global scale, accounting for approximately 20% of the world's electricity. China is currently world's largest producer of hydroelectricity, mostly because of its massive Three Gorges Dam, and similar big hydropower projects.

The largest hydroelectric power plant in the world is Three Gorges Dam in China, with the capacity of 22.5 GW, the second ranked is Itaipu Dam, located between Brazil and Paraguay with the capacity of 14 GW, and the third place belongs to Guri Dam, located in Venezuela, with the capacity of 10,2 GW. Since huge hydroelectric power plants can often result in environmental problems small and micro hydro projects are becoming increasingly popular on global scale.

Huge hydroelectric power plants can have negative impact on environment if not thoroughly planned and carefully constructed. Hydropower dam construction can change stream levels, flow patterns, temperature of the water, all of which can have very harmful effect on nearby wildlife.

BIOMASS

Biomass belongs to renewable energy sources, and refers to biological material deriving from living, or recently living organisms such as wood, waste or biofuels. Biomass has many different forms, but most of these forms are different plant matter grown to generate electricity or produce heat. There are five different energy resources from which the biomass derives: wood, waste, garbage, landfill gases, and alcohol fuels.

Biomass is abundant source of energy that can be found in almost every corner of the world. Biomass also helps decrease the CO2 emissions despite the fact that burning of the biomass does in fact release CO2 just like the burning of fossil fuels. Biomass because of its availability could be an excellent energy option for developing countries which would help them reduce the dependence on foreign fuel import and improve their energy security. Especially since it does not require highly advanced technologies.

Biomass also releases CO2 emissions, though it does not contribute to global warming like fossil fuels do because burning of biomass which releases CO2 emissions practically balances the CO2 absorbed by the plants during its growth. Biomass is also significantly more expensive than coal, and it needs to improve economics in years to come.

Biomass is becoming increasingly popular energy source on global scale, with many countries opening new biomass facilities. Wood is still the most popular form of biomass on global level, though there are many ongoing researches that aim to find the adequate solutions to turn waste and garbage into useful form of energy.

Biomass currently satisfies around 4% of US energy needs, and half of this comes from using wood which remains the most popular form of biomass in US. According to the recent numbers the currently existing biomass power generating industry in the United States has the capacity of around 11,000 MW.

The largest biomass power plant in United States is The New Hope Power Partnership, Florida with the capacity of 140 MW. Biomass power plant size is often driven by biomass availability in close proximity as transport costs of the fuel play a key factor in the plant's economics.

Unlike solar, wind or geothermal energy biomass is connected with CO2 emissions that contribute to climate change, though it has to be said that these emissions are significantly smaller than the ones coming from fossil fuels because plants during their growth absorb CO2 which in the end compensates for the CO2 coming from the biomass burning. Since wood is the most common form of biomass, unsustainable biomass production could also lead to deforestation.

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